New kitty throwing up

I just got a kitty yesterday from the humane society. She is 10 weeks old. She was fine yesterday afternoon and night. Then this morning when we woke up she had thrown-up a few times. Then she threw up a few more times and now its all liquid.
She is drinking water. I called the humane society and they said that it was probably stress from the new environment and to try a little bit of wet food. Well thats been a 2 hours ago and she hasn't touched it. She has been sleeping most of the day, but gets up and runs around every so often.
Also she is still pooping in her litter box. The vets not open since its Sunday. Should I take her to the vet ER?

Did the humane society give you some of the food she had been eating? Food changes can cause digestive upset. You could try to finger feed her a bit to get her to eat something. If she's still not eating but is drinking, I'd take her to the vet first thing in the morning. If she's not eating or drinking, I'd call the ER vet and see whether they recommend bringing her in (make sure you tell them her age).

I called the ER vet and they said to make sure she stays hydrated and if it continues take her to the vet on Monday. Well she is drinking water and just ate a little of the wet food that I gave her. The wet food has little chunks of chicken in it is that ok?

Sorry your new baby is throwing up. My orphaned kittens are 10 weeks also.
One of mine had problems throwing up and I used unflavored pedialyte. Sometimes mixed the broth only from chicken soup (no onions in soup).

Offer some kind of liquid very often even if only a little is taken.

You can mash the canned chunks with a fork and add liquid to make it soupy.
They may eat it better that way.

Someone with more experience will respond. These wonderful people helped me get my orphans this far!